there's several failure points on these. I don't know how much they play into one another but I had a green color transistor that I ran with a jumper wire for the last year, and about 2 weeks ago the monitor started spazzing out, losing the color bias information a lot, and if you tried adjusting the color levels in the OSD, you could see on the test pattern with color bars that the green had some weird artifacting in it whenever I changed ANY of the colors.
I replaced the transistor with a new one, not because the one that was in it was bad, but because the legs weren't already cut... I had to do some trace scraping, soldering that, bending the leg that way, etc. and well... all seems fine now. prior to that I was changing the factory menu shit like every 3 days.
I replaced all the transistors and corresponding resistors on the neckboard on this one and another D9200 that had intermittent missing red. red's supposedly the one that fails the most. it's not a tube thing, it's all in the neckboard. there was a recall on the neckboard, which if I'm not mistaken led to the creation of the D9400, somewhat of a bug-fixed D9200. those came with flat CRTs too, I think.
but yeah, Chad at Arcadecup told me that sometimes the drive transistors will get extremely hot and just burn out, other monitors won't even have this problem. another strange happening is that the yoke retaining clip will melt off, and the yoke will slide all the way down to the neckboard.
if you have way of fitting some kind of cooling device on the monitor, go for it. you can turn the color drives down in the factory menu too, they won't run as hot. the image quality might suffer a tad, but you won't toast anything that way.
anyway, long story short, after I fed you the long story, I think in addition to the IC getting corrupted sometimes, that if all the other electronics have any sort of problems, it'll cause the monitor to go batshit too. it's not necessarily a BAD monitor, it just has crap quality, Wells had some people in Korea make them, and they were of noticeably inferior build quality to the U2000/K7500/U3000s they made before, but this one's a one size fits all application, which is why MAME people like them.